By Dan Zinkand
Veteran strip-tiller Tom Oswald of Cleghorn, Iowa, wants to find a happy medium between tilling the soil and having soil become so loose and fluffy that it undermines corn standability.
"There is a clear interaction between different corn-hybrid root-architecture types and root lodging," says Oswald, who’s been strip-tilling for 15 years. “This is particularly true when the soil strength is broken by tillage with little re-compaction.
Tom Oswald on his Cleghorn, Iowa farm. Oswald has been strip-tilling for 15 years.
"I've noticed this a number of times over the years. We sometimes have — and just missed by 30 miles in 2010 — rolling downdraft storms that hit from late July into August."
"Depending on when a wind event hits, it can cause significant yield reduction from root lodging,” Oswald says. “Post tassel, the plant doesn’t stand up much, if at all. As a result, the corn plant, as a solar collector, is compromised and harvest losses can be great."
A friend of Oswald who strip-tills had to harvest corn in one direction due to root lodging caused by such a storm in 2010.
"He observed that the whole rootball of certain hybrids tipped in the loose strip," Oswald says. "The most compacted rows of a strip system are the pinch rows between the duals and end rows. Both areas seemed to stand better for him."
Oswald says his friend ordered less-aggressive knives for his strip-till machine — mini-mole knives instead of regular mole knives — because damage from the 2010 storm had him looking for ways to reduce lodging risk.
"I have experienced similar things myself," Oswald says. "In 2006, we had a very nasty storm hit Cherokee County, where I farm in northwest Iowa. It was a mess for a lot of people. The worst fields were those where guys did significant deep tillage with little re-compaction — it didn’t seem to matter if it was full-width tillage from rippers and manure injectors, or controlled-traffic strip-till.
"From the air that year, you could see diagonal patterns where corn was standing a bit better in spring-tillage tractor tracks — including those from tracked tractors — like I saw in other years when those violent wind events hit fields with low soil strength."
The key tillage benefit of strip-till is not fluffy, loose soil for crop plant growth, Oswald says. It’s the ability to get more consistent conditions for planter performance, year-in and year-out, with warming due to the reduced moisture and soil darkness in the strip.
"The soil starts warming after tillage breaks the soil particle connections that drive capillary moisture movement," Oswald says. "Wet soil doesn’t warm up readily, so with fall strip-till some of that tillage benefit is gone. The soil is clearly mellow and loose in the strip, but I would suggest that the dryness and warming is less than a similar spring strip due to reconsolidation."
The problem with spring strips formed with a knife or shank is that strips are not always mellow — even if the soil is loose and dry, Oswald says. This can vary greatly due to the degree of freezing and thawing over winter, and the degree of surface compaction if wet soils are present at harvest.
"Farmers like soft, fluffy soil because of historical and cultural tillage mindsets, but I would suggest that fluffy soil is not always good for crop establishment," Oswald says. "Roots need good soil contact for moisture and nutrient uptake. Fluff is difficult to manage because you really don’t know where you are until the soil reconsolidates. It will eventually, but it’s hard to predict to what degree."
Oswald’s strip-till toolbar began as a DMI 3200, with nine knives and 36-inch-row spacings in a sidedress configuration. He eventually extended the toolbar to 12 rows with 30-inch spacing. He added a liquid system for 10-34-0 or 7-21-7, which allows him to dual-place fertilizer with ammonia, or strip-till 28% liquid nitrogen depending on the conditions.
Oswald pulls the strip-till rig with a 190-horsepower Case IH MX 210 tractor equipped with Trimble EZ-Steer, EZ-Guide 500 and OmniStar XP correction.
Time For Trials
To study problems with cornfield lodging, while continuing to reap the benefits of strip-tilling and indexed fertilizer placement, Oswald has two replicated strip-trial experiments for 2011.
First, after strip-tilling in the fall of 2010, he ran an old Brillion culti-mulcher over 12-row swaths to physically reconsolidate comparison strips. In another field, Oswald established a trial with 24-row areas of "online" and "offline" strip placement.
"Since 2008, I have reasonably accurate GPS steering," he says. "I established a replicated study with my normal strip-till swaths (where the planter units will run on the fall strip-tilled zone) while skipping swaths that I filled in with my strip-till line offset by about 10 inches. By doing this, the corn row will land on the shoulder of the offset strip-tilled zone when following the normal A-B line at planting. This is an intermediate soil strength area."
With screw-adjust Dawn residue wheels, Oswald says he can fine-tune the residue clearing to achieve similar row-residue levels between trial conditions.
"This field is reasonably well drained with good tile, so I should be able to plant the same day "on" or "off" the strip," he says. "In both trials, I may even experiment with hybrids that have "good" and "less good" root ratings, in a split-planter fashion, to see if there’s a difference in case we get a storm."
For 2011, Oswald also established trials to compare fall strip-tilled soybeans on 30-inch row spacings to his standard no-tilled soybeans on 30-inch row spacings following corn. He tried this years ago and found the strip-till soybeans lodged and yielded less due to excessive growth. But with the lower populations and varieties Oswald uses now, he wonders if strip-tilled soybeans will stand and yield better.